1. Field of the Invention
The present invention relates to a laser diode module for optical communication, and more particularly to a laser diode module for optical communication employing a superlattice microcooler.
2. Description of the Related Art
As is generally known in the art, a semiconductor laser device is made of a semiconductor device that is based on a P—N bonding structure and employs quantum electron concepts. In particular, a semiconductor laser diode emits light corresponding to reduced energies produced from the recombination of vacancies and holes. The recombination of vacancies and holes are induced intentionally by applying current into a thin film, i.e., an active layer, composed of semiconductor materials.
The semiconductor laser diode has certain characteristics. For example, being small in size, in comparison with a solid laser such as a He—Ne laser or an Nd—YAG laser, and being able to control the intensity of light through controlling current. Semiconductor laser diodes which have such characteristics have been employed as light sources for optical recording devices and optical restoring devices, when they have a low output and short wavelength. And, they have been employed as light sources for optical communication, when they have a long wavelength. Also, in the case of high output, they have been employed as excitation devices for solid laser devices such as an Nd—YAG laser.
In regard to an optical module for communication, it is very important to control the wavelength. Moreover, it requires an additional structure to remove heat produced during the activation of the optical module and the temperature increase produced from the surrounding temperature is moved toward the outside of the package quickly, in order to achieve the proper wavelength control.
As a result, several packaging structures and methods have been suggested, wherein heat produced during the activation of the optical device is quickly discharged to the outside in order to meet such requirements.
The laser diode module is an integrated body having a laser diode light source fixed to a head and incidental devices, such as a cooler for cooling the laser diode, a photo detector for sensing output of the laser diode, and a temperature sensor for sensing the temperature of the whole head, are additionally disposed on the head.
Generally, in regard to the semiconductor laser diode module, a heat sink wherein a laser diode chip is loaded, is provided with (1) a cooling device such as a thermoelectric cooler, etc., (2) a thermistor for detecting heat, and (3) a photo diode for sensing light from the chip are provided with the laser diode module incidentally.
FIG. 1 is a schematic cross-sectional view of a conventional laser diode module for optical communication. FIG. 2 is a shows the construction of the thermoelectric cooler in FIG. 1.
Referring to FIG. 1, in regard to the laser diode module for optical communication. a plurality of leads (not shown) protruding sideward are provided in the lower surface of the laser diode module, and a housing 10 formed with sidewall protruding to a certain height from the upper surface thereof constitutes a basic frame of the laser diode module. Further, a thermoelectric cooler (TEC) 11 is fixed to a central portion of the upper surface in the housing 10 with a cooling side thereof facing toward upper direction, and a heat sink 12 having a certain height is provided at the cooling side of the thermoelectric cooler 11 for absorbing heat emitted from a laser diode 15. Also, a submount 13 is provided on the heat sink 12, and the laser diode 15 is supported by a first submount 14 and a photo diode 17 is supported by a second submount 16 are fixed on the submount 13. A lens 18 is also disposed on the submount 13 to collect laser beams emitted from the laser diode 15.
Thermoelectric cooler (TEC) 11 has a structure as shown in FIG. 2, wherein a plurality of P type and N type pins 23, e.g., 20 to 50 pins, are provided between the cold side (active cooling) 21 and the hot side (heat rejection) 22 of the cooler.
However, in regard to the conventional thermoelectric cooler, the plurality of pins are assembled manually and thereby results in manufacturing process complexity and high production costs, which makes it difficult to achieve a low cost laser diode module for optical communication. Additionally, the thermoelectric cooler is too large in size to be installed through micro optical subassembly (OSA), such as a mini-plat requisite to optical transmitter/receiver (Tx/Rx) and a TO-can package, etc.